For a sample of what this course will include, see the video "Energy, Environment, and Everyday Life MOOC with University of Illinois Professor David Ruzic" - http://go.citl.illinois.edu/Energy-MOOC
This course teaches you everything you need to know about energy, the environment, and at least a number of things in everyday life. It starts by talking about energy itself and where it comes from. This includes how much we have, who has it, who uses it, and what that all means. The video clips are produced in a fast-paced multimedia format during which Professor Ruzic throws in fun and demonstrations. There are multiple-choice questions to check your understanding and some more in-depth exercises to guide you deeper into the subject.
After explaining the main things we use energy for – our cars and electronics! – fossil fuels are examined in detail. Want to really learn about fracking or pipelines? Watch these segments. The environmental effects of fossil fuels are taught as well. Global warming, acid rain, and geoengineering all are in this part of the course. Part of their solution is too. Renewables follow, with clips on solar, wind, hydro, geothermal, biofuels, etc. You’ll even see Professor Ruzic in a corn field and in the middle of a stream showing how you could dam it up.
Finally, nuclear power is taught in detail – how it really works and what happens when it doesn’t work, as in Three Mile Island, Chernobyl, and Fukushima, as well as how we are making it today, which is shown here without political preconceptions. In this course, economics takes center stage. People will ultimately do whatever costs the least, so energy policy is most effective when it is targeted at the user’s wallet.
Throughout the course there are 24 segments on “How Things Work." These guides to everyday life are tremendously varied, covering everything from fireworks to making beer to what happens backstage at a theater. The course is designed to be enjoyable as well as informative. We hope you will take a look!

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À partir de la leçon

Week 1: How It All Starts and Ends

The course starts by looking at the basic principles of energy sources at the level of the atoms and molecules. This shows how everything from wind energy to nuclear energy share the same basic concept. We then go on to blow some stuff up and explain the statistics of what forms of energy are used around the world – who has them, who uses them, and who produces them. “How Things Work” segments start with a bang (fireworks) and then get both louder (bell towers) and softer (silencers).

Enseigné par

David N. Ruzic

Abel Bliss Professor

Transcription

[MUSIC] This is all great stuff. One of the places where people always think about soundproofing is every time you watch some spy movie. And you watch this and the great James Bond-type hero comes in and sneaks in to some place. There's 50 armed guards and takes out the pistol with the silencer and manages to shoot them one at the time and the others are totally ignorant of this fact, because they can't possibly hear the gun shot going off because of the silencer. Well it's not really called a silencer, except by you and me. The people who know this stuff call it a suppressor. And they call it that because it doesn't really make it silent. It certainly makes it less noisy. [SOUND] >> Go. [SOUND] Subsonic rounds. [SOUND] >> So how does it work? How do you actually make a gun, one of the loudest things around turn into something quieter? Well, this unit that is screwed on to the end of the barrel is as many as the same principles. Not the computerized ones but rather the baffle structure. There are three things that make noise in a gun. The first is when you actually discharge the bullet. You have a mechanical hammer that strikes the firing pin which initiates the gunpowder exploding. Very hard to do anything about that, there's going to be some kind of clicking mechanical sound, but that's actually pretty quiet, all right? The second thing, that makes a gun loud is that the bullet is actually going to break the sound barrier. That's where the quack, comes from. It's a tiny little sonic of boom of that bullet going too fast. That's also pretty much impossible to suppress unless you buy bullets that have less gunpowder and specifically never propel the bullet faster than the speed of sound. Don't worry, those bullets are still plenty dangerous, all right. They're just not faster than the speed of sound, 1,100 feet per second, 350 meters per second. If you have bullets that go slower than that you won't hear the crack. But most of the noise is because the exploding gases that are propelling the bullet come out of the gun barrel and you basically have just heard an explosion. So you're going to hear a lot of compressional waves as this stuff hits the air and transmits that sound to your ear. So what we can do with these expanding gases is we first divert them in other places. And then we do this over and over. So whatever gases do come through this hole, that they're still expanding, they go up here, they go up here, they go up here and the amount of hot gas that comes out is much less. These can have a variety of styles, right. Here's another case where you have series of baffles and you can extend this farther and farther and farther. Now keep in mind, the explosive gases coming out of a gun are very hot. You've just blown up a significant amount of gun powder or other type of explosive. And these types of suppressors won't last forever. They're going to get hot because they're absorbing that hot gas. You can have replaceable sections even, where you can repair your suppressor if you've used it too much. The effect of this is to take a gun shot which is typically around 160 decibels. I should explain a moment what a decibel is. It's a unit of how intense that sound wave is, how much power is in that sound wave. And for every 10 decibels, that power, that energy that was transmitted per unit time, for every 10 decibels goes down a factor of 10. So something at 150 decibels has 10 times less power. Now is it ten times less quiet? Depends what you mean by quiet. We don't have a really good way in our ears to describe this. I can't say, hey my voice is this and now I'm going to double the loudness of my voice. Is this double the loudness? Or is that significantly higher? You really need a decibel meter to find out. So 10 times less the power is every range of 10, turns out that a good suppressor can take this from 160 to 130. Now, 130, this would be 1,000 times less power. But it's probably the amplitude that really pushes your eardrum and that goes as the square root of the power or I should say the power is the square of the amplitude. So this is about 31 times less amplitude. And that is a significant quiet. This, 160, without your protection or something, this causes permanent damage. And in fact, 130 is pretty close to that range as well, this still can cause pain. Anything above this is definitely painful to your ears. So, 130 decibels, it's like a trumpet about this far from your ear. Still loud, nothing like this though, completely softer. But not so soft that if someone shoots a gun with a suppressor, you're going to be able to say, boy, I just hear birds tweeting and not look over that way. You might wonder then why are they useful or exist? Well, this is still significantly less. And the other thing is, the gunshot is short. You just hear a staccatic, probably quite a bit louder than that. You might not clue into it as loud as if you've actually heard the trumpet a half meter away from you because the trumpet's sound is going to be much longer, probably as long as the person playing it is going to play. Let's actually go to a soundproof room and listen. So I'm here with Chad Wahls. >> It's nice to meet you. >> And he is the Facilities Manger at the School of Music and he's going to teach us about soundproofing. So, what we're doing here is to make a place that's really quiet because you don't want to hear all that outside stuff. You actually put a room inside a room. So of course you've got the door to the outside room and you have the door to the inside room and between them, of course, you have more soundproofing material, mass, things that damp those sound waves. And as you come in here and as we get everyone in and shut the door, you probably will even hear a difference. Now when we're talking, we have no background noise. So Chad, what do they do in this facility? >> This facility was built in 1968, so the construction methods were a little different back then. This building is built on mass. >> Okay. >> What we do is we have two courses of concrete walls, or concrete cinder block that's very hard and then we fill it with sand in between. >> And the sand damps the sound waves, right? >> Yeah. >> The sound doesn't really go well through sand. >> Yes, right. >> It's a lot of tiny little particles. >> And it has more mass so things don't move. >> Okay. >> Other places in the building, like our studios, our teaching studios, we have sheet rock on top of plaster coursing. And then there's a piece of Z metal in between there to actually absorb anything that the sheet rock moves before it actually hits that structure. >> That's right, since sound waves is actually material moving, making those compressional waves in the air. If you have stuff that doesn't move at all, then it can't make any more sound as it goes. >> That's correct. So we absorb as much energy as possible before we transfer it to the structure. >> So this room itself, what do people do in it? >> This is part of our experimental music studios. This is where we create and mix down all of our multi-channel stuff. >> So by mixing that means you don't want any outside sound. You want to control what's going to go on to the recording. >> That's correct. You want to be able to come back to a repeatable controlled environment anytime. >> And I notice there's some of these foam stuff on the wall. >> Yes. >> But not everywhere. >> No. >> And that's intentional, right? >> That's correct. You want to have some reflection in the room. If the room is too dead, then you can't really get an accurate representation of what it's going to do in the outside and it's also rather eerie feeling whenever a room is completely dead. People in big, nice anechoic chambers, people have been known to get anxiety and literally lose their minds. >> Wow, that sounds like fun. >> It's documented, I read it online. It was pretty cool. But they have a couple overseas that are just amazing. They're so quiet people can't be in them for very long. >> Okay, and you have something like that here, right? >> We have a room that I accidentally made too quiet. >> Okay. >> It's part of our testing center and I feel that it's too quiet. People like it when they're testing. If you're reading and concentrating on something, it's not bad. But if you're in there, you don't want to be in there for long. It's just really dead and quiet. >> That'd be interesting? So, what did you call this stuff again? >> This is Auralex. >> Auralex? >> Auralex. >> Like in aura, A-U-R-A, aura. >> It is a trade. >> It really looks like foam rubber. >> It is, Auralex is a trade name but it becomes something like, I don't know, this is my chevy type of thing. But it comes flat packed like this, it's cut, it comes apart and its basically absorption. So we do several things, this room doesn't have much diffusion. We do absorption, diffusion and reflection. We have gobos downstairs in our recording studio that we record in that's got absorption on one side and diffusion on another side, reflection on another. We can go. >> What is a gobo? >> We call them gobos because we move them around, and then we can spin them. >> They're movable platforms with stuff on them? >> Yeah, they're very movable, so we can build little rooms inside of rooms with them, and so like a recording booth or something like that. If we want to put a vocal mic in one, or an instrument in another, we can isolate them to a degree. >> This is the things you'd put on the room, we get this sound absorbing shape. The little cells inside the foam itself is what will actually damp the sound, take away the sound energy and put it in to heat really, I think that's a heat. And the shape of this is such that if there's a wave that reflects, it really gets trapped, it doesn't reflect very well. So if you completely cover the walls with a material like this you'll get no bounce back, you'll get no reflection back. And that's where you get that eerie kind of, too dead of a sound. >> And the absorption is due to the, well, it is important to calculate your depth because your wavelength has to do with that. So twice the effectiveness of this is twice this wavelength, for the most part. >> Okay, twice the wavelength of the subject thickness. >> Of the thickness of the material. That's where it's going to be most effective. >> Okay. >> So it's not really going to do much for very low frequency reflection. >> Right, because low frequencies are very, very long wavelength. And that's the places where you need the foam stuff that sticks out several feet. >> And that's where mass helps in our building. Now it's not going to keep the reflection down but the mass helps keep the low frequency abated so it doesn't get into the other environment. >> Right. So this room is too quiet? >> This room is too quiet. So if you're concentrating on something in here and you're doing your testing, it's fine. But if you spend too much time, even now you can feel it, it feels stuffy and uncomfortable. >> Let's try to be real quiet here. Yes, I can see. >> [LAUGH] >> And even the air, I mean, it kind of seems like there's no air, but there is. >> There is air coming through. >> There's air, through the vent. >> A lot of air and humidity. >> A lot of air and humidity. It's just that we've got too much. So we got the absorbent stuff on the wall because of course the hallway is where the noise like come from. And what's in these panels? >> This is actually fiber glass on a frame. It's, I think it's a 3M product that we use or that they use. You can make them yourself and it's pretty neat. But we bought these for our auditorium and recording studio. We had some leftover, somebody wanted the room quiet, I was like, hey I've got this leftover, let's put it in this room. >> Yeah. >> Put too much in. >> And this does the same thing that the foam we're looking at. >> That's correct. That's correct. So, it's a little thicker. >> So you get a larger spectrum wavelengths. >> And you can tell by your voice, it's a little bit boomier in here because it's not that it's making it boomy, it's taking everything out but the boom. >> Except for the lowest sound. >> That's correct. That's correct. >> So if we go real low that's going to actually. >> It will make it really resonate. >> Right. Man this is fun stuff. >> [LAUGH] >> Who knew trying to be quiet was so hard. That's what you need to know about sound and how to get rid of it. [MUSIC]